Differential expression profiles and gene structure of two tumor necrosis factor-α variants in Atlantic salmon ( Salmo salar L.)

Here we present the gene structure and expression data on two Atlantic salmon TNF-α genes. Both genes are approximately 2.0 kb in length and organized into four exons and three introns. The open reading frame of both genes translates into 246 amino acid putative peptides, being 91.5% identical at the amino acid level. The upstream regulatory region of both genes were amplified by inverse PCR and analyzed for putative regulatory binding sites. Variant specific gene-expression both in vitro and in vivo revealed that the two variants are differentially regulated. TNF-α2 is the dominant variant throughout the experimental period following LPS stimulation of TO-cells. The picture was different in head kidney tissue following vaccination of Atlantic salmon with an experimental multivalent oil-based vaccine. TNF-α2 was the most dominant transcript in the non-stimulated controls and in the early phase. A shift from TNF-α2 to TNF-α1 was however seen, and from day 12 the TNF-α1 was most abundant transcript. Implications of variant specific gene-expression are discussed.